ALIEN-KILLING BOYZ IN THE ‘HOOD: Director Joe Cornish’s band of London teen hoodlums beat back an alien invasion, not to mention sci-fi summer movie disappointment, in Attack the Block.

Anyone who's watched his share of alien invasion movies knows there's a certain dramatic protocol for how humankind's initial extraterrestrial encounters work. There's a bright flash in the night sky, and a ship (or pod, or meteor, or what have you) lands in some underpopulated area. Through either bravery or ill fortune, a small investigating party appears, and, if they're lucky enough to be the protagonists, the first contact ends with them successfully running for their lives. If they're less successful, they're likely some poor saps in some other invasion flick billed only as "Farmer" or "Errant Birdwatcher."

The situation should some slimy cocoons happen to be aimed at South London is rather different, according to Joe Cornish's Attack the Block. A pig-sized beastie crashes into a parked car, then slices a young boy's cheek as it flees into the darkness. The kids from Super 8 might have run home to wring hands; the kids in Attack the Block chase and corner the critter, bludgeon it to death, and then drag it through the rainy streets back to their apartment complex.

It's a fun subversion that sets the tone for what follows. These five pubescent hoodlums (led by newcomer John Boyega as Moses) eventually become the saviors of the block, but first they use their trophy to bother some neighborhood girls and bring it to their weed dealer (Shaun of the Dead's Nick Frost) for safekeeping and cable-TV zoological diagnosis. The boys lie to their parents, menace strangers, and jump at the chance to run back out to murder more aliens. Yet Cornish manages to one-up everyone else on the recent Amblin nostalgia kick, despite the fact that we like the main characters only slightly more than the bloodthirsty "gorilla-wolf motherf--ers" they encounter.

Beating Super 8 at its own game, then, earns Attack the Block a spot among the very best of 2011, all because it's the most focused, creatively authentic action-horror flick in recent memory. Playing like early John Carpenter by way of a Spike Jonze music video, Attack the Block is so well orchestrated as a close-quarters invasion movie that we end up keeping our story expectations to ourselves, no matter how familiar the scenario. It's a key trait of all the best genre cinema, and it informs nearly every aspect of Attack the Block's production.

Take the special effects design: Though the boys' initial kill is given a low-key, shadowy reveal, the creature doesn't bear much resemblance to the "gorilla-wolves" that terrorize the block, so we again anticipate the big reveal—until that gets a little complicated. The effects team's work on the aliens is remarkable to begin with, but the concept surrounding them is doubly effective, with the side effect of chiding us for our expectations even as it acquits itself structurally to the action film.

Subversion aside, what really puts Attack the Block across as a miracle of urban sci-fi is the polish that rookie writer/director Cornish brings to the table. The script is funny, well-considered, and formally airtight; there aren't any scenes, details, or characters that don't serve the story. The pacing is confident and even at a sleek 88 minutes, and the tone accommodates every laugh and thrill. Cornish's work behind the camera echoes the causal skillfulness of his friend and executive producer Edgar Wright, but even Wright's own terrific films (most recently Scott Pilgrim vs. the World) couldn't exist without their pop-culture references, whereas Attack the Block is beautifully self-contained. Is Joe Cornish automatically a filmmaker on the level of Wright, or J.J. Abrams? It's impressive enough that the question comes to mind.

However it happened, the important thing about Attack the Block is that it's as fun from start to finish as any of the best sequences this summer had to offer. (Think Magneto vs. Kevin Bacon.) It's not often that a flawless bit of entertainment comes around—I couldn't even think of a second exemplary scene just now—and before long we'll be into dreary old Oscar season. Attack the Block is the only movie this year that beat my summertime blues.